This invehtion relates to a method and apparatus for monitoring the physiological characteristics of a subject. In particular, it relates to a method and apparatus for detecting changes in the body's cardiovascular and respiratory systems innervated by the autonomic nervous system without requiring the attachment of sensors to the body of the person being examined.
Instrumentation is available for detecting and measuring relatively small changes in brain wave patterns, heart activity, skin conductivity, breathing activity and other physiological properties. However, in general, such devices have the disadvantage that sensors must be attached to the body of the subject being tested. In the case of burn victims, it is desirable to have a continuous record of vital signs, but electrodes often cannot be placed on the skin. In other situations, such as when persons are undergoing intensive medical care, suffering mental distress, exhibiting unreasonable behavior, working in a high-stress environment or require monitoring for long periods of time for any reason, the reaction of the subject to the attachment of sensors to his body can affect the measurements to such an extent that the validity of the evaluation is substantially reduced.
Accordingly, it is an object of the invention to provide a method and apparatus for monitoring physiological changes in a subject without attaching wires or other devices to his body.
Another object is to permit monitoring a subject under conditions in which he is not aware he is being examined.
Still another object is to provide apparatus for physiological monitoring that is relatively simple to use and inexpensive to manufacture.